Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
  • G02B7/28—Systems for automatic generation of focusing signals
  • G02B7/34—Systems for automatic generation of focusing signals using different areas in a pupil plane
  • G02B7/346—Systems for automatic generation of focusing signals using different areas in a pupil plane using horizontal and vertical areas in the pupil plane, i.e. wide area autofocusing
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
  • H04N23/95—Computational photography systems, e.g. light-field imaging systems
  • H04N23/951—Computational photography systems, e.g. light-field imaging systems by using two or more images to influence resolution, frame rate or aspect ratio
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14601—Structural or functional details thereof
  • H01L27/1462—Coatings
  • H01L27/14621—Colour filter arrangements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14601—Structural or functional details thereof
  • H01L27/14625—Optical elements or arrangements associated with the device
  • H01L27/14627—Microlenses
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
  • H04N23/60—Control of cameras or camera modules
  • H04N23/69—Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
  • H04N23/80—Camera processing pipelines; Components thereof
  • H04N23/84—Camera processing pipelines; Components thereof for processing colour signals
  • H04N23/843—Demosaicing, e.g. interpolating colour pixel values
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
  • H04N25/10—Circuitry of solid-state image sensors [SSIS]; Control thereof for transforming different wavelengths into image signals
  • H04N25/11—Arrangement of colour filter arrays [CFA]; Filter mosaics
  • H04N25/13—Arrangement of colour filter arrays [CFA]; Filter mosaics characterised by the spectral characteristics of the filter elements
  • H04N25/134—Arrangement of colour filter arrays [CFA]; Filter mosaics characterised by the spectral characteristics of the filter elements based on three different wavelength filter elements

Definitions

• the present invention relates to an image generation method, and an image generation apparatus.
• the exit pupil of the imaging lens is divided into multiple pupil areas, and multiple
• parallax images corresponding to the divided pupil areas can be captured at the same time.
• US Patent No. 4410804 discloses an image capture apparatus that uses a two-dimensional image sensor in which one microlens and multiple divided photo-electric converters are formed with respect to one pixel.
• the divided photo-electric converters are configured so as to receive light from different pupil sub-areas of the exit pupil of the imaging lens via one microlens, and thus pupil division is performed.
• the multiple parallax images that are captured are equivalent to light field (LF) data, which is information on a spatial distribution of light intensity and an angle distribution.
• LF light field
• An image generation method for generating an output image from an input image acquired by an image sensor that has an array of a plurality of pixels, each of which has arranged therein a plurality of sub-pixels that each receive a light beam that passes through a different pupil sub-area of an imaging optical system, the method including: a step of generating a plurality of parallax images that respectively correspond to the different pupil sub-areas based on the input image; a step of generating a plurality of pixel shifted images by performing different non-integral shifting for each of the plurality of parallax images according to a virtual image forming plane of the imaging optical system that is different from an image sensing plane at which the image sensor is arranged; and a step of generating an output image that has a higher resolution than each
• a program causes a computer to execute the steps of the above-described image
• a computer-readable storage medium stores a program for causing a computer to execute the steps of the above-described image generation method.
• an image generation apparatus comprises an image sensor configured to acquire an input image, wherein the image sensor has an array of a plurality of pixels, each of which has arranged therein a plurality of sub-pixels that each receive a light beam that passes through a different pupil sub-area of an imaging optical system; a first generation means configured to generate a plurality of parallax images that respectively correspond to the different pupil sub-areas based on the input image; a second generation means configured to generate a plurality of pixel shifted images by performing different shifting for each of the plurality of parallax images according to a virtual image forming plane of the imaging optical system that is different from an image sensing plane at which the image sensor is arranged; and a composition means configured to generate an output image that has a higher resolution than the resolution of the parallax images from the plurality of pixel shifted images through composition processing.
• FIG. 1 is a schematic configuration diagram of an image capture apparatus according to embodiments of the present invention.
• FIG. 2 is a schematic diagram of a pixel array according to embodiments of the present invention.
• FIGS. 3A and 3B are a schematic plan view and a schematic cross-sectional view of a pixel
• FIG. 4 is a schematic diagram for
• FIG. 5 is a schematic diagram for
• FIG. 6 is a schematic diagram of a
• FIG. 7 is a diagram for describing a
• FIG. 8 is a flowchart of image generation according to a first embodiment of the present
• FIG. 9 is a diagram for describing pixel shift in parallax images according to embodiments of the present invention.
• FIG. 10 shows an example of a relational expression between an output image and a pixel shifted image according to embodiments of the present invention.
• FIG. 11 is a flowchart of image generation according to a second embodiment of the present
• FIG. 1 is a configuration diagram of a camera as an image capture apparatus that has an image sensor according to a first embodiment of the present
• reference numeral 101 denotes a first lens group arranged at the leading end of an imaging optical system, and this lens group is held so as to be capable of moving forward and backward in the optical axis direction.
• Reference numeral 102 denotes an aperture/shutter that not only adjusts the amount of light in image capturing by performing opening diameter adjustment, but also functions as a shutter for
• Reference numeral 103 denotes a second lens group.
• the second lens group 103 can move forward and backward in the optical axis direction together with the aperture/shutter 102, and realizes a magnification effect (zoom function) by moving in conjunction with forward/backward movement of the first lens group 101.
• Reference numeral 105 denotes a third lens group that adjusts the focal point by moving forward and backward in the optical axis direction.
• Reference numeral 106 denotes an optical low-pass filter, which is an optical element for reducing false coloring and moire that appear in captured images.
• Reference numeral 107 denotes an image sensor configured by a two-dimensional CMOS photosensor and peripheral circuitry, and this image sensor is arranged at the image forming plane of the imaging optical system.
• Reference numeral 111 denotes a zoom actuator that performs a magnification operation by driving elements from the first lens group 101 to the third lens group 105 in the optical axis direction by rotating a cam barrel (not shown) .
• Reference numeral 112 denotes an aperture/shutter actuator that adjusts the amount of captured light by controlling the opening diameter of the aperture/shutter 102, as well as controls the light exposure time in still image
• Reference numeral 114 denotes a focus actuator that adjusts the focal point by driving the third lens group 105 forward and backward in the optical axis direction.
• Reference numeral 115 denotes an electronic flash for subject illumination in image capturing, and is preferably a flash illumination apparatus that uses a xenon tube, but may be an illumination apparatus that includes a continuous-emission LED.
• Reference numeral 116 denotes an AF auxiliary light apparatus that projects a mask image having a predetermined pattern of openings into the subject field via a projection lens so as to improve focus detection capability with respect to darks subjects and low-contrast subjects.
• Reference numeral 121 denotes a CPU in the camera that performs various types of control with respect to the camera body, has an arithmetic portion, a ROM, a RAM, an A/D converter, a D/A converter, a communication interface circuit, and the like, and drives various circuits in the camera based on a predetermined program stored in the ROM.
• This CPU also executes a series of .operations such as AF, image capturing, image generation, and recording.
• the CPU 121 is an image generation means, a parallax image generation means, a pixel shifted image generation means, and a super-resolution processing means of the present invention.
• Reference numeral 122 denotes an electronic flash control circuit that performs control for lighting the electronic flash 115 in synchronization with an image capturing operation.
• Reference numeral 123 denotes an auxiliary light driver circuit that performs control for lighting the AF auxiliary light apparatus 116 in synchronization with a focus detection operation.
• Reference numeral 124 denotes an image sensor driver circuit that controls image capturing operations of the image sensor 107, as well as subjects an acquired image signal to A/D conversion and
• Reference numeral 125 denotes an image processing circuit that performs processing such as ⁇ conversion, color interpolation, and JPEG compression on an image that was acquired by the image sensor 107.
• Reference numeral 126 denotes a focus driver circuit that adjusts the focal point by
• Reference numeral 128 denotes an aperture/shutter driver circuit that controls the opening diameter of the aperture/shutter 102 by
• Reference numeral 129 denotes a zoom driver circuit that drives the zoom actuator 111 in accordance with a zoom operation that was performed by a photographer.
• Reference numeral 131 denotes a display apparatus such as an LCD that displays information regarding the camera shooting mode, a preview image before image capturing, an image for checking after image capturing, an image indicating the focus state in focus detection, and the like.
• Reference numeral 132 denotes an operation switch group that is configured by a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like.
• Reference numeral 133 denotes a
• FIG. 2 is a schematic diagram of a pixel array and a sub-pixel array in the image sensor of the present embodiment.
• FIG. 2 shows a 4x4 pixel array range in the pixel array and a 16*16 sub-pixel array range in the sub-pixel array in the two-dimensional CMOS sensor
• the present embodiment describes an image sensor that has a pixel period ⁇ of 20 m and an effective pixel count NLF of approximately 2.2
• pixels 200G that have G (green) spectral sensitivity are arranged as pixels at diagonal positions, and a pixel 200R that has R (red) spectral sensitivity and a pixel 200B that has B (blue) spectral sensitivity are arranged as the other two pixels.
• ⁇ ⁇ ⁇ (a 4x array of) sub-pixels 201 to 216 are arranged in a two-dimensional array in each pixel.
• FIG. 3A is a plan view of one of the pixels
• FIG. 3B is a cross-sectional view of the same pixel taken along a-a in FIG. 3A and viewed from the -y side.
• the pixel 200G of the present embodiment is provided with a microlens 305 for focusing incident light on the light-receiving side of the pixel, and is provided with photo-electric converters 301 to 316 that are divided into ⁇ areas
• converters 301 to 316 respectively correspond to the sub-pixels 201 to 216 in FIG. 2.
• the photo-electric converters 301 to 316 may be pin-structure photodiodes in which an intrinsic layer is sandwiched between a p layer and an n layer, or, as necessary, may be pn-junction photodiodes in which the intrinsic layer is omitted.
• a color filter 306 is formed between the microlens 305 and the photo-electric converters 301 to 316. Also, for each sub-pixel, the spectral transmittance of the color filter may be changed, or the color filter may be omitted, as necessary .
• FIGS. 3A and 3B is focused by the microlens 305, filtered by the color filter 306, and then received by the photo-electric converters 301 to 316.
• each photo-electric converter pairs of an electron and a hole are generated according to the amount of received light and separated by a depletion layer, and then negatively charged electrons are accumulated in the n layer (not shown) , whereas the holes are discharged outside the image sensor via the p layer, which is connected to a constant voltage source (not shown) .
• FIG. 4 is a schematic diagram showing the correspondence relationship between pupil division and the photo-electric converters 301 to 316 (sub-pixels 201 to 216) .
• FIG. 4 is a cross- sectional view of the pixel 200G shown in FIG. 3A taken along a-a and viewed from the +y side, and shows the exit pupil face of the imaging optical system.
• the x axis and the y axis in the cross-sectional view are the opposite of those in FIGS. 3A and 3B in order to correspond to the coordinate axes of the exit pupil face.
• the image sensor is arranged in the
• pupil sub-areas 501 to 516 are in an approximately conjugate
• the exit pupil 400 of the imaging optical system is divided in Np
• a pupil area 500 is the pupil area from which the entire pixel 200G can receive light when all of the photo- electric converters 301 to 316 (sub-pixels 201 to 216) that are divided into ⁇ ⁇ ⁇ areas (4x areas) are combined.
• FIG. 5 is a schematic diagram showing the correspondence
• the photo-electric converters 301 to 316 In each pixel of the image sensor, the photo-electric converters 301 to 316
• an input image is acquired by the image sensor that has an array of multiple pixels, each of which has arranged therein multiple sub-pixels that each receive a light beam that passes through a different pupil sub-area of the
• a parallax image that corresponds to a specified pupil sub-area among the pupil sub-areas 501 to 516 of the imaging optical system can be obtained by, for each pixel, selecting a signal from a specified sub-pixel among the sub-pixels 201 to 216 (photoelectric converters 301 to 316) .
• a specified sub-pixel among the sub-pixels 201 to 216 photoelectric converters 301 to 316.
• parallax image that corresponds to the pupil sub-area 509 of the imaging optical system can be obtained by selecting the signal from the sub-pixel 209 (photo- electric converter 309) for each pixel. The same follows for the other sub-pixels as well. Based on the input image acquired by the image sensor of the present embodiment, multiple (pupil division count Np) parallax images that respectively correspond to the different pupil sub-areas and have a resolution equal to the effective pixel count can be generated.
• a captured image with a resolution equal to the effective pixel count can be generated by adding together all of the signals from the sub-pixels 201 to 216 for each pixel.
• FIG. 6 is a schematic diagram of the
• ⁇ is the angular resolution
• ⁇ be the estimated elevation of the exit pupil of the imaging optical system
• the sub-pixels 212 to 209 receive light beams that have angles of incidence ⁇ 0 to ⁇ 3 respectively. Light beams whose angles of incidence have a range of the angular resolution ⁇ enter the sub-pixels .
• FIG. 7 is a schematic diagram for
• the i- th pixel Xi light beams that entered at the angles da
• LF data which is information on a spatial distribution of light intensity and an angle distribution, can be acquired, and the LF data is constituted by multiple parallax images respectively corresponding to the different pupil sub-areas as described above.
• a refocused image can be generated at a virtual image forming plane by translating all of the sub-pixel signals Li, a along the respective angles Qa from the image sensing plane to the virtual image forming plane, distributing the signals to virtual pixels in the virtual image forming plane, and then performing weighted addition.
• the coefficient used in the weighted addition is determined such that all of the values are positive and have a sum of 1.
• the exit pupil of the imaging optical system having the aperture value F decreases in area upon being divided into ⁇ ⁇ ⁇ pupil areas, and the effective aperture value of the pupil sub-areas increases to NGF.
• the third member in Expression (1) shows that refocusing can be performed in the range in which the effective aperture value NGF of the pupil sub-areas increases and the focal depth increases.
• step S100 an input image is acquired by the image sensor that has an array of multiple pixels, each of which has arranged therein multiple sub-pixels (the sub-pixels 201 to 216) that each receive a light beam that passes through a different pupil sub-area of the imaging optical system. It is also possible to use an input image that was captured by the image sensor having the above configuration in advance and stored in a recording medium.
• step S200 a parallax image that
• the imaging optical system corresponds to a specified pupil sub-area among the pupil sub-areas 501 to 516 of the imaging optical system is generated by, for each pixel, selecting a signal from a specified sub-pixel among the sub-pixels 201 to 216 from the input image. Based on the input image, multiple parallax images that respectively correspond to the different pupil sub-areas and have a resolution equal to the effective pixel count are generated .
• step S300 multiple pixel shifted images are generated by, for each of the parallax images generated in step S200, performing different non- integral shifting according to a virtual image forming plane of the imaging optical system that is different from the image sensing plane at which the image sensor is arranged.
• FIG. 9 is a diagram for describing pixel shift in parallax images. Although the following describes only the x direction for the sake of
• An image is generated by, for each pixel, selecting the sub-pixel signal Li, a that entered at the a-th angle 9a, and that image is the parallax image that corresponds to the a- th pupil sub-area.
• multiple pixel shifted images are generated by performing translation along the angle 6a for each of the parallax images to a virtual image forming plane that is different from the image sensing plane.
• a distance d between the image sensing plane and the virtual image forming plane is set such that the amount of shift in the horizontal direction is a non-integer.
• step S400 super-resolution processing is performed such that an output image whose resolution is higher than the resolution of each of the parallax images is generated from the multiple pixel shifted images that were generated in step S300.
• FIG. 9 shows the relationship in the
• Expression (2) is a relational expression between the super-resolution pixel signal 1 ⁇ and the sub-pixel signal 1. ⁇ arrayed one-dimensionally .
• step S400 an output image (super- resolution pixel signal ⁇ , ⁇ ) is generated through super-resolution processing for obtaining the inverse matrix ⁇ _1 ⁇ , ⁇ , ⁇ ', ⁇ ' of the determinant ⁇ , ⁇ , ⁇ ', ⁇ ' and performing compositing using the relational expression of Expression (4).
• the inverse matrix ⁇ _1 ⁇ , v, ⁇ ' , v' may ⁇ be obtained in advance as necessary.
• a configuration is possible in which, as necessary, the super-resolution pixel signal ⁇ , ⁇ , the inverse matrix ⁇ _1 ⁇ , , ⁇ ' , ' , and the sub-pixel signal ⁇ , ⁇ , ⁇ in Expressions (3) and (4) are respectively subjected to Fourier transformation, super-resolution processing is performed in the frequency space, and then inverse Fourier transformation is performed.
• dark correction As necessary, dark correction, shading correction, demosaicing processing, and the like may be performed on one or a combination of the input image, the parallax images, the pixel shifted images, and the output image.
• the present embodiment is one example of an image capture apparatus that has an image generation means for performing the above-described image
• the present embodiment is one example of a display apparatus that has an image generation means for performing the above-described image generation method.
• a captured image that has a high spatial resolution can be generated from multiple parallax images.
• the processing up to the generation of multiple parallax images that respectively correspond to the different pupil sub-areas and have a resolution equal to the effective pixel count based on the input image in step S200 is similar to that in the first embodiment .
• step S310 translation along the angle 9a is performed for each "x direction only" parallax image, and multiple x-direction pixel shifted images are generated by performing x-direction non- integral shifting (shifting by the non-integral factor 1/ ⁇ of the pixel period ⁇ ) .
• step S410 multiple x-direction super resolution images are generated by solving the
• Expression (5) can be explicitly described as the recurrence formulas in Expressions (6a) to (6d).
• the recurrence formulas in Expressions (6a) to (6d) can be sequentially solved for the super-resolution pixel signal ⁇ , ⁇ , and there is no need to obtain the inverse matrix ⁇ _1 ⁇ , ⁇ ' of the determinant ⁇ , ⁇ ', thus making it possible to simplify the arithmetic processing. In this way, x-direction super-resolution processing is performed through steps S310 and S410.
• step S320 translation along the angle Gb is performed for each "y direction only" x- direction pixel shifted image, and multiple y-direction pixel shifted images are generated by performing y- direction non-integral shifting (shifting by the non- integral factor 1/ ⁇ of the pixel period ⁇ ) .
• step S420 the recurrence formulas expressing the relationship between the y-direction pixel shifted images and the super-resolution pixel signal ⁇ , ⁇ are sequentially solved for the super- resolution pixel signal ⁇ , ⁇ , and thus an output image (super-resolution pixel signal ⁇ , ⁇ ) is generated.
• a captured image that has a high spatial resolution can be generated from multiple parallax images.
• aspects of the present invention can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described
• the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiments.
• the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (e.g., computer-readable medium) .

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